A construction machine generally has a function of cooling fluid, which is a cooling object, such as engine cooling water or hydraulic oil. Specifically, a construction machine is provided with a radiator and/or oil cooler for exchanging heat between the cooling water and/or hydraulic oil and the outside air. Such a construction machine involves a risk of overcooling of the cooling water and hydraulic oil in the case of the operation under cold conditions where the outside air temperature is low (for example, below freezing point).
Conventionally known is a construction machine provided with means for adjusting the flow rate of cooling air flow passing through the radiator or oil cooler, as described in Japanese Unexamined Patent Publication No. 2008-37343 (Patent Document 1) and Japanese Utility Model application Publication No. H4-82318 (Patent Document 2).
Patent Document 1 discloses a construction machine including a radiator with an opening, a louver installed on the radiator so as to be able to open and close the opening, and a radiator grille device having a drive means for driving the louver in the open/close direction. The louver is held in a close position when at least one of the water temperature and oil temperature is lower than respective set temperatures for them, and is shifted to an open position when both of the water temperature and the oil temperature are higher than the respective set temperatures.
Patent Document 2 discloses a construction machine provided with a shut device having a plurality of vanes which can be opened and closed so as to switch between a fully-open state and a fully-closed state, and a cylinder which moves each of the plurality of vanes. The vanes of the shut device are opened and closed in accordance with the cooling water temperature of the engine, thereby change the flow rate passing through the radiator.
The installation of the radiator grille device and/or the shut device, however, involves the increase in the size of the construction machine because of securing the space for the installation. Besides, for compactly slewing construction machines it is difficult to create space for the additional installation of the radiator grille devices and/or shut devices.